Analysis of structure-function relationships on smooth muscle myosin using NMR and X-ray crystallography.

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Myosin is an enzyme transducing the chemical energy from the hydrolysis of ATP into directed mechanical movement, in conjunction with actin. In this research, we use the NMR, which is a good probe to observe the microenvironments, and X-ray crystallography, which allows us a precise three-dimensional structure determination, to investigate the mechanism of energy conversion by myosin with atomic level.From the pH- and temperature-dependent changes of the signals in the ^<31>P-NMR spectra of smooth muscle sub fragment 1-ADP complex, it is appeared that the interaction between the smooth muscle myosin subfragment 1 and ADP is stronger than that of skeletal muscle myosin subfragment 1 and ADP. In the case of kinesin and ncd motor domains, it was found to exist two different forms of motor domain-ADP complex. In addition, we found a difference between kinesin and ncd motor domains in the chemical shift of the a-phosphate of bound ADP, indicating that the electrostatic or magnetic microenvironments of this site of these motor domains differed from each other.We established the baculovirus expression system to obtain the recombinant chicken gizzard smooth muscle myosin motor domain as well as mutants for crystallization. We also found that the role of the neck region on the ATPase activity of kinesin.